Translated from French using Google Translate.

French:
Source

Pallet is an Academy Award-nominated composer, violinist, keyboardist, and vocalist. He does most of his work with other artists as an instrumentalist/violinist though.

EDIT: Apparently, he worked with her before on "The Last Time" from Red. He's listed in the album's credits and personnel pages:

violinist

Originally posted by TayLord didn't someone in the base say a couple of days ago taylor should do a song with a violin being the main instrument?

Oh, he worked with her on Red before. From Red's "credits and personnel":

Originally posted by intheneonlights He worked with her on "The Last Time"

Originally posted by intheneonlights He worked with her on "The Last Time"

Owen Pallett – conductor, orchestration

Originally posted by intheneonlights He worked with her on "The Last Time"